The content of Application No. 99810884.9, filed Sep. 30, 1999, in Europe, is hereby incorporated by reference.
The present invention concerns a tool head that can be mounted on a machine tool headstock and fitted with a radially movable tool holder slide. Such a tool head allows the machining of cylindrical portions that are external or internal, coaxial, of different diameters, as well as of circular or truncated plane faces, with a single machining tool.
Different tool heads able to perform a machining of this type are known from the prior art.
The company Komet in Besigheim, Germany, supplies a tool head of this type comprising a first slide that can be moved perpendicularly to the axis of rotation of the tool head and that carries the machining tool, as well as a second slide to compensate unbalance and that can also be moved perpendicularly to the axis of rotation of the tool head. The mass of the second slide is equivalent to the sum of the masses of the first slide and of the tool it carries. Both slides are driven in opposite directions by a tension rod fitted with a double rack acting simultaneously on the two slides. This device has at least to major disadvantages, namely that the force necessary to act on the tension rod depends essentially on the centrifugal force exerted on the two slides, i.e. on the head""s speed of rotation as well as on the radial position of the two slides. Consequently, use of such a tool head is limited at low machining speeds. The other inconvenience is caused by the play of the rack on the slides toothing, thus limiting the machining accuracy.
Other tool heads propose to have the machining tool swivel on an eccentric circle. Such a method means that the working angle of the tool on the work piece varies during machining, which is detrimental for the state of the worked piece""s surface.
U.S. Pat. No. 4,508,475 of Peuterbaugh describes a tool head with two slides, the pressing means on the slides being constituted by springs. This document does not specify anywhere a relation between the pressing forces exerted by the springs and those exerted by the centrifugal force.
The hydraulic pressing means described in patent U.S. Pat. No. 5,307,714 of Muendlein et al. acts on the longitudinal actuator rod for moving the slides and not directly on the slides themselves. There is thus no compensation of the centrifugal force on the slides as sought.
A first object of the invention is therefore to propose a tool head able to perform a machining as proposed without the aforementioned inconveniences of known tool heads.
Another object of the invention is to propose a tool head that can perform a machining as proposed and whose force driving the means for radially displacing the tool is independent from the speed of rotation of the head as well as from the radial displacement of the tool.
Another object of the invention is to propose a tool head that can perform a machining as proposed and whose driving means for radially displacing the tool are free from play.
Another object of the invention is to propose a tool head that can perform a machining as proposed and that is of simple construction, reliable and requiring minimal maintenance.
According to the invention, these objects are achieved by a tool head as described in claim 1, variants or alternative embodiments being described in the dependent claims.
An embodiment of the invention is described hereafter, this description making reference to the attached drawings containing the figures and in which: